Print hammer control means for pivotally mounted-type members

ABSTRACT

A printer has a plurality of print hammers which impact pivotaltype levers carried by type carriers moving along a track adjacent the print line. Cam surfaces on the body of the carrier cooperate with portions of the print hammer to prevent interference between the print hammer and an adjacent type lever when printing.

[ 1 Feb. 8, 1972 United States Patent Drejza a t e u u 1 s 0 6 9 1 9 9 3 1 5 2 3,224,366 12/1965 Cunningham. Antonnucci.

3,379,125 4/1968 3,416,442 12/1968 Brownetal....

[72] Inventor: John E. Drejza, Endwell, N.Y.

3,451,335 6/1969 Cunningham...................:::..

[73] Assignee: International Business Machines Corporatiou, Armonk, N.Y. Primary Examiner-william B. Penn Dec. 22, 1969 Appl. No.: 887,203

Att0rneyHanifin and Jancin and Francis V. Giolma [22] Filed:

[57] ABSTRACT A printer has a plurality of print hammers which impact pivotal-type levers carried by type carriers moving along a 93 C track adjacent the print line. Cam surfaces on the body of the 9,14 B41] 9/28 carrier cooperate with portions of the print hammer to -101/93 Q93 93-114 prevent interference between the print hammer and an adjacent type lever when printing.

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0 d d mm 11 8 55 11 [52] US. Cl.

7 Claims, 8 Drawing Figures References Cited UNITED STATES PATENTS PATENTEUFEB em 3,640,217

SHEET 1 [1F 3 INVENTOR JOHN E. DREJZA t a a W I} M ATTORNEY PATENTED FEB 8 I972 SHEET 2 BF 3 muli m m/ m FIG. 4

FIG.

PATENTED FEB 8 E72 SHEET 3 UF 3 PRINT HAMMER CONTROL MEANS FOR PIVUIALLY MOUNTED-TYPE MEMBERS CROSS-REFERENCE TO RELATED APPLICATIONS This invention is related to and is an improvement over the invention of copending application, Ser. No. 884,953 of James M. Cunningham, filed Dec. 15, 1969.

1. Field of the Invention This invention relates generally to high-speed printers and it has reference in particular to chain/train printers of the front printer type.

2. Description of the Prior Art Heretofore, printers having leveror finger-type carrying elements moving past a row of print hammers have relied on a sufficiently slow rate of type element movement to permit withdrawal of a print hammer after printing and prevent interference between the print hammer and the type elements.

SUMMARY OF THE INVENTION Generally stated, it is an object of this invention to provide an improved high-speed front printer.

More specifically, it is an object of the present invention to prevent interference between the print hammers and adjacent type levers in a chain/train printer of the front printer type.

Another object of this invention is to reduce the occurrence of shadow printing in a front printer of the chain/train type.

It is also an object of the present invention to permit higher speed operation of the chain/train in a front printer.

Yet another object of the invention is to reduce wear in the chain/train of a front printer.

Still another object of the invention is to prevent breakage of the type levers in a chain/train front printer.

According to a preferred embodiment of the invention, a plurality of type carriers, each having one or more pivotaltype levers for impacting a document as the carrier slides on a rail past a plurality of print positions, are provided with projecting cam surfaces associated with each type lever. The type levers are impacted by pivotal print hammers having corresponding cam surfaces which coact with those of the type carriers to facilitate return of an actuated print hammer without any interference with an adjacent type lever.

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawing.

DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a partial schematic showing of one type of printer apparatus with which the invention may be used.

FIG. 2 is an enlarged partial view in side elevation of a print hammer, type carrier, and type lever showing an application of the invention.

FIG. 3 is a cross-sectional view along the line 33 of FIG. 2.

FIG. 4 is a rear elevational view of the type carrier in FIG. 2 with the type levers and pivot removed for purposes of clarity.

FIG. 5 is a bottom plan view of the type carrier of FIG. 4.

FIG. 6 is an enlarged schematic partial plan view of a plurality of type levers and print hammers embodying the invention of FIG. 2 showing how excessive type wear is prevented and prevents shadow printing by coming in too early and hitting type to the right of one to be hit.

FIG. 7 is an enlarged schematic partial plan view of a plurality of type levers and print hammers embodying the invention of FIG. 2 showing how shadow printing is prevented, and

FIG. 8 is an enlarged schematic partial plan view of a plurality of type levers and print hammers not embodying the invention showing how catastrophic failure could occur without the protection afiorded by the present invention.

I 2 DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 shows a printer apparatus of one type with which the present invention may be used and comprises a Type Cartridge 10 having a plurality of individual Type Carrier Elements l1 movable in a continuous path on a Stationary Frame 12. A portion of the path of the motion of the Type Carrier Elements 11 includes a straight portion along which printing can occur and which hereinafter is referred to as the print line. Each Type Carrier Element 11 has one or more different engraved characters on the surface thereof adjacent the print line. Plural sequences of type characters are obtained by assembling 'the Type Carrier Elements 11 in predetermined arrangements on the Frame 12. The Type Carrier Elements 11 are drivenpreferably in the form of a train along the Frame 12 so that they travel at a constant velocity and are maintained in abutting relation along the straight portion of the path of travel.

The printer apparatus of FIG. 1 is a front printer, but is generally similar to the back printer, which is described in detail in U.S. Pat. No. 3,241,480, which issued on Mar. 22, 1966, to James M. Cunningham, and in accordance with wellknown operational principles thereof, a Paper Document or Form 13-is posiu'oned behind an Ink Ribbon 14 or the like, which in turn is positioned immediately adjacent the Type Carrier Elements 11 along the print line portion thereof.

The Ribbon 14 may be fed in any suitable manner as between Spools 15 (only one of which is shown) along the line of travel of the Type Carrier Elements 11. The Paper Document l3,however, is fed transversely to the direction of motion of the Type Carrier Elements 11. Guide Bars 17 and 18 and Carriage Forms Feed Tractors coact to support and move the Paper Document 13 in the proper line of travel. Generally, printing occurs while the Paper Document 13 is stationary relative to the print line. On completion of a print cycle the Paper Document 13 is advanced one or more spaces by the Carriage Tractors 19 to a position where a new line of data may be printed. A means for feeding the Paper Document 13 in synchronism with operation of the print mechanism is well known inthe art and may include a Carriage Drive Motor 22 or the like, connected to Shafts 20 by means of Pulleys 21 or the like, or the Carriage Tractors 19.

As shown in FIG. 1, printing occurs when a pivotally mounted Finger Ila of a selected one of the Type Carrier Elements 1 l is impacted against the Ribbon 14, Paper Document 13, and a Platen 23 associated therewith. The impacting occurs at various print positions along the print line to eventually form a complete line of data. For this purpose a plurality of Print Hammers 24 are mounted beneath the Cartridge l0 and in front ofthe depending Type Character Bearing Fingers or Levers 1 laof the Type Carrier Elements 1 l, which are guided by a Guide Rail 12a of the Frame 12, as shown in FIG. 2. The Type Carrier Elements 11 are retained on the Guide Rail 12a by a CoverPlate 12b or the like, in front of the Print Medium 13. Print Hammers 24 are arranged to be uniformly spaced so that one Print Hammer 24 occupies each print position along the print line, and the Hammers 24 are aligned in a single row parallel to the print line. Each Print Hammer 24 is a part of an individualhammer unit, which comprises an Electromagnet 26 with an. Armature 28 and a Push Rod Connector Element 30 with Bias Springs 32, which maintain the Hammers 24 out of contact with the Type Fingers Ila, when the Electromagnets 26 are deenergized. Each Hammer 24 is individually operable and the operation of the various Hammers 24 occurs selectively at random positions along the print line in accordance with instructions from suitable control means (not shown), which comprises a type-tracking device and a coacting storage device, which indicates the particular data to be printed. Further details of a suitable control system may be more fully understood by reference to a patent such as U.S. Pat. No. 2,993,437 of F. M. Demer and E. .l. Grenchus for a High Speed Printer, which issued July 25, I96].

As shown in FIGS. I and 2, printing is designed to occur when a Print Hammer 24 is actuated by its Print Rod 30 to rotate about a Support Pivot to impact a selected Type Character Bearing Finger or Lever illa against the Ribbon I4 and the Document 13, which is backed up by a Bar or Platen 23. As shown more particularly in FIG. 2, each Type Carrier Element 11 comprises an inverted chair-shaped slug having spaced apart upwardly extending legs 11c and 11d, which define a Groove lle, which receives a Rail 12a of the Frame Member 12 along which the Type Carrier Elements 11 are guided. A Cover Plate 12b secured in a suitable manner retains the Type Carrier Elements 11 on the Rail 12a. The Vertical Leg Portion 11d of the Type Carrier Element 11 is provided with a plurality of slots or Grooves 11f in which depending Type Bearing Fingers 11a are pivotally mounted by a Pivot llg. Teeth 11h are provided on the rear of the Vertical Leg 11d for driving the Type Carrier Elements 11 as explained in the Cunningham patent hereinbefore referred to.

Since the Type Carrier Elements 11 are moving along the Rail 12a carrying the Type Levers 11a past the different Harnmers 24, it will be realized that problems may be encountered by reason of possible interference between the Type Bearing Fingers 11a and the Print Hammers 24. In order to minimize such interference and improve the quality of printing, spaced Cam Members lli are provided on the Vertical Leg Portion 11d of the type carrier as shown in FIGS. 2, 4, and 5, being, for example, formed on an Insert llj. These Cam Members lli may be in the nature of raised ribs, which are positioned on either side of each of the Type Bearing Fingers llla for engaging a corresponding Cam Member 24a on the Print Hammer 24. As shown, each of the Cam Members lli and 24a have inclined surface portions. The Cam Members lli of the Type Carrier Element I1 define a Recess 11k therebetween, which is wide enough to receive the corresponding Cam Member 240 of the type hammer, to permit the Hammer 24 to actuate the associated Type Lever 11a, when the Hammer 24 and Type Lever 11a are in the proper mating relationship. The Cam Members lli and 24a are positioned so that they engage just prior to actual printing. As it is preferable to keep the Cam Members within the normal confines of the Type Carrier Elements l1, the Cam Member 24a is positioned offcenter in the opposite direction to the motion of the Carrier. The angle on the leading edges of the Cam Members lli and 24a is reduced to less than that of the trailing angle to reduce the acceleration forces on the Hammers during camming action.

In FIG. 6 is shown the manner in which the invention functions to protect the Type Levers 11a from excessive wear. The dashed lines 2AA represent the relative position (dark-filled section A) of a Hammer 24 when it is at the nominal relative location with respect to a Type Lever 11a for optimum wear conditions. The solid line 248 represents the relative location of a Hammer 24 when the timing is such that the minimum allowable overlap for no wear occurs. It can be seen (assuming that the Hammer 24 and Type Lever lla are moving at about the same velocity in the directions shown) that under each of these conditions (and all conditions between) the Hammer 24 will be allowed to push the Type Lever 11a out of alignment with the other type levers and cause printing without any interference between the Hammer Cam Member 24a and the Carrier Cam lli at the shaded area B. However, should the Hammer 24 try to arrive any earlier (to the right of the position shown solid) an interference would occur at the area B wherein the Hammer 24 would be prevented from striking the Type Lever 11a, thus, preventing printing with too little overlap. FIG. 6 also shows that printing of a character to the right of the one selected (early nipping or shadow printing) is impossible since the Cam Member 24a again prevents contact with the adjacent Type Lever ll la bearing that character.

In FIG. 7 there is shown the manner in which the invention prevents shadow printing (late nipping) of the character to the left of the one selected to print. The shaded area C shows how the potential for nipping is developing should the Hammer 24 be timed to strike late and, thus, stay in line of interference too long. Shaded area D shows how the Cam lli on the Type Carrier Element 11 will act on the Cam Member 24a of the Hammer and cam the Hammer 24 out to prevent nipping.

FIG. 8 shows how a catastrophic failure could occur without the benefits of the invention. The shaded area E shows that a positive interference (no protection from cam surfaces) could develop if the Type lla were allowed to move too far out of the type line. This could occur if the Platen 23 was not positioned close enough to the type line. The same type of interference could develop in the event a Type Finger 11a breaks and leaves a void in the line of type so that the Hammer 24 is fired into the void.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a printer having a type carrier element movable along a print line past a plurality of print positions on a document and carrying one or more type members movable relative to said carrier element transversely of the direction of motion of said carrier element to impact said document for printing thereon,

a plurality of print hammers positioned in print positions along said print line selectively operable from a rest position in a direction transversely of said print line to an operated position to impact selected type members and move them against the document as they pass along said print line, and

cam means on the carrier element positioned on opposite sides of each said type member along the line of motion of said carrier member to engage a portion of one of said print hammers which is in said operated position, when said print hammer is other than in proper alignment with a selected type member in the direction of motion of said carrier element and cam said print hammer toward its rest position.

2. The invention as defined in claim 1 characterized by said type carrier having a plurality of closely spaced apart type members comprising type levers pivotally mounted on a pivot shaft extending in the direction of motion of said type carrier element.

3. The invention as defined in claim 2 characterized by said type carrier element having inclined cam surface projections on said carrier element located on either side of a preferred type lever impact position with a print hammer.

4. The invention as defined in claim 3 characterized by said cam members on the carrier element being spaced apart further than the width of the engaging portion of said type hammer to allow lateral movement in the direction of motion of said carrier element of said selected type lever relative to said type hammer between the time of initial impact with said print hammer and the time of printing by said type lever impacting said document.

5. The invention as defined in claim 4 characterized by said engaging portion of said type hammer comprising a cam member with a sloping surface which is displaced from the center of said type hammer in the opposite direction to the direction of movement of said type carrier element.

6. The invention as defined in claim 5 characterized by said cam member on said type hammer having unsymmetrical leading and trailing inclined cam surfaces, said trailing cam surface having a greater angular inclination than said leading cam surface.

7. The invention as defined in claim 6 characterized by said type carrier element having raised cam members on said carrier element positioned between each of said type levers carried by said carrier element and having oppositely disposed inclined plane surfaces along the line of movement of said type carrier element. 

1. In a printer having a type carrier element movable along a print line past a plurality of print positions on a document and carrying one or more type members movable relative to said carrier element transversely of the direction of motion of said carrier element to impact said document for printing thereon, a plurality of print hammers positioned in print positions along said print line selectively operable from a rest position in a direction transversely of said print line to an operated position to impact selected type members and move them against the document as they pass along said print line, and cam means on the carrier element positioned on opposite sides of each said type member along the line of motion of said carrier member to engage a portion of one of said print hammers which is in said operated position, when said print hammer is other than in proper alignment with a selected type member in the direction of motion of said carrier element and cam said print hammer toward its rest position.
 2. The inveNtion as defined in claim 1 characterized by said type carrier having a plurality of closely spaced apart type members comprising type levers pivotally mounted on a pivot shaft extending in the direction of motion of said type carrier element.
 3. The invention as defined in claim 2 characterized by said type carrier element having inclined cam surface projections on said carrier element located on either side of a preferred type lever impact position with a print hammer.
 4. The invention as defined in claim 3 characterized by said cam members on the carrier element being spaced apart further than the width of the engaging portion of said type hammer to allow lateral movement in the direction of motion of said carrier element of said selected type lever relative to said type hammer between the time of initial impact with said print hammer and the time of printing by said type lever impacting said document.
 5. The invention as defined in claim 4 characterized by said engaging portion of said type hammer comprising a cam member with a sloping surface which is displaced from the center of said type hammer in the opposite direction to the direction of movement of said type carrier element.
 6. The invention as defined in claim 5 characterized by said cam member on said type hammer having unsymmetrical leading and trailing inclined cam surfaces, said trailing cam surface having a greater angular inclination than said leading cam surface.
 7. The invention as defined in claim 6 characterized by said type carrier element having raised cam members on said carrier element positioned between each of said type levers carried by said carrier element and having oppositely disposed inclined plane surfaces along the line of movement of said type carrier element. 